This was discussed before. I believe we determind it was like this from the factory. It is oily and chunky, almost like Tapioca. It was only there at first flush and never after that. I think we assumed it had something to do with the assy. process. At any rate, normal, goes away after you flush the systema and no damage has resulted.
It is in the same category as that "clunk" you hear on take-off. Nobody knows what is causing it and it's normal.